jQuery.extend({
	screen : function( opt ) {
		if(opt === undefined) opt = {};	
		opt.t == 'undefined' ? 500 : opt.t;
		$('body').append($('<div id="screen" style="position:absolute;top:0;left:0;background:#000;z-index:9998;filter:alpha(opacity=0);opacity:0;display:none;"></div>'));
		$('#screen').show().animate({
			'opacity':0.4
		},opt.t).css('width',$(document).width()).css('height',$(document).height());
	},
	unScreen : function( opt ) {
		if(opt === undefined) opt = {};
		opt.t == 'undefined' ? 500 : opt.t;
		$('body').append($('<div id="screen" style="position:absolute;top:0;left:0;background:#000;z-index:9998;filter:alpha(opacity=0);opacity:0;display:none;"></div>'));
		$('#screen').animate({
			'opacity':0
		},opt.t,function() {
			$('#screen').hide();
		})
	}
})
